Catalytic degradation of water micropollutants and LED-assisted decolourisation of Sudan dyes via mycosynthesised gold nanoparticles

Synthetic dye wastes and pollutants found in industrial effluents are escalating the threat to water resources. As a solution, catalytic degradation of water micropollutants by biologically synthesised nanoparticles has garnered considerable attention due to their eco-friendly nature. This study reports the synthesis of gold nanoparticles from an aqueous fungal extract of Talaromyces purpureogenus and their potential to degrade various synthetic dyes and pollutants. At optimised biosynthesis parameters, precursor concentration (0.6 mM), pH (7), temperature (30 degrees C), and reaction time (24 h), surface plasmon resonance was observed near 530 nm, and the resultant AuNPs were characterised. Transmission electron microscopy revealed particles of irregular shapes of 16-40 nm. The reduction and capping were attributed to the presence of alcoholic/phenolic groups, carbonyl groups, amines, and amides. The catalytic efficacy of the AuNPs was demonstrated by the decolourisation of 14 compounds, including thiazine, azo, xanthene, triarylmethane dyes, and nitroaromatics, and the corresponding degradation rate constants (k) were calculated. The AuNPs degraded > 90% of all dyes, except Sudan III and IV, following pseudo-first-order kinetics. To enhance the degradation of Sudan III and IV, a combined treatment involving exposure to a blue light-emitting diode (LED) was employed. A four-fold increase in k values for Sudan III and three-fold for Sudan IV was observed at a maximum LED intensity of 200 mW/cm2. The degradation rate was intensity-dependent, evidenced by the linear correlation of k values with the LED intensity. These findings provide a sustainable way to clean up the water resources. {GRAPHIACAL ABSTRACT}